Greylisting

Your box using a technique called greylisting to cut down on spam. Greylisting works by delaying mail from people you haven’t received mail from before for up to about 10 minutes. The vast majority of spam gets tricked by this. If you are waiting for an email from someone new, such as if you are registering on a new website and are waiting for an email confirmation, please give it up to 10-15 minutes to arrive.

+tag addresses

Every incoming email address also receives mail for +tag addresses. If your email address is you@yourdomain.com, you can also accept mail at you+anythinghere@yourdomain.com. Use this as a fast way to create aliases or to segment incoming mail for your own filtering rules.

Use only this box to send as you

Your box sets strict email sending policies for your domain names to make it harder for spam and other fraudulent mail to claim to be you. Only this machine is authorized to send email on behalf of your domain names. If you use any other service to send email as you, it will likely get spam filtered by recipients.

Relaying for other machines

If you have other machines on domains that are under the jurisdiction of your Mail-in-a-Box and they need to send mail (e.g. a webserver, or any machine that has cron jobs you want to see the output of) it is recommended that you configure those machines to relay via the Mail-in-a-Box.

If the remote machine is running Ubuntu 14.04 this can be done by applying the following steps to it:

1. Run sudo apt-get install postfix and choose “Satellite system” when prompted.
2. Append the following seven lines to /etc/postfix/main.cf:

   mydestination = 
   smtp_use_tls = yes
   smtp_tls_security_level = verify
   smtp_tls_CAfile = /etc/ssl/certs/ca-certificates.crt
   smtp_sasl_auth_enable = yes
   smtp_sasl_password_maps = hash:/etc/postfix/relay_password
   smtp_sasl_tls_security_options = 

3. Write credentials in the following form to /etc/postfix/relay_password (substitute the second and third values with credentials for a freshly created account on the Mail-in-a-Box):

   {{hostname}} username:password

   The account that you create on Mail-in-a-Box for this purpose can be on any of the domains that your Mail-in-a-Box manages, as the only requirement on mail sent by the remote machine is that it is from a domain that the Mail-in-a-Box manages. You may wish to create aliases on Mail-in-a-Box so that any replies sent to automatically generated messages do get routed to your own inbox; otherwise they will accumulate in the inbox of the relay account.
4. Finally, chmod it to 600 (sudo chmod 600 /etc/postfix/relay_password), run sudo postmap /etc/postfix/relay_password and then reload postfix (sudo service postfix reload).

That's it! Mail created and dispatched on the remote machine will now be routed via your Mail-in-a-Box.